Photographic material



, from the light fog due to an undesired exposure.

United States Patent 3,251,691 PHOTOGRAPHIC MATERIAL JozefFrans Willems and Gerard Michiel Sevens, Wilrijk- Antwerp, Belgium, assignors to Gevaert Photo-Producten N .V., Mortsel, Belgium, a Belgian company No Drawing. Filed Sept. 21, 1961, Ser. No. 139,599

6 Claims. (Cl. 9652) The present invention relates to fog inhibiting compounds and stabilizers for light-sensitive photographic emulsions and also to the use of these compounds in light-sensitive photographic material.

It is known that light-sensitive photographic emulsions, on storage in a place of a high temperature and a high relative humidity or wherein these materials come into contact with some substances such as hydrogen sulphide, hydrogen peroxide vapours or reducing agents, tend to lose their sensitivity and become spontaneously developable Without any preliminary exposure. This phenomenon is called chemical fog as to differentiate it The fog formation depends on the emulsion type and is directly proportional to the age, the temperature and the relative humidity on storage.

It is also known that the silver image formed after exposure undergoes a degradation, by which is meant a shift and a decrease of intensity of the image tone during the finishing to a visible image e.g. under the influence of ingredients used in the developing bath, the fixing bath, the colouring bath, and so on. This'degradation especially appears on drying the developed images, whereby a decrease of density and of gradation and the appearance of an undesired colour or metallic gloss of the developed silver, the so-called plumming, is stated.

This phenomenon is particularly pronounced when thephotographic images are submitted to hot glazing. Several compounds have been proposed to be used as stabilizers, fog-inhibiting agents or antibronzing agents. The greater part of these compounds, however, presents the draw-back of being only active within Well definite limits andof usually exerting a strong desensitizing action onto the emulsion.

It has now been found that the compounds of the class of the 4,5-substituted oxazoline-2-thione(s) corresponding to the following general formula:

R NH

wherein: each of R and R (equal or ditferent) represents' an alkyl radical, a substituted alkyl radical, an aryl radical, a substituted aryl radical, an alkaryl radical or a substituted alkaryl radical, or together represent the atoms necessary to represent a cyclo-aliphatic ring structure are effective anti-'bronzing agents and exert a stabilizing and a fog-inhibitingaction onto the lightsensitive photographic emulsions without impairing the sensitivity. As compounds of this type may be mentioned e.g.:

4,5 -d.imethyloxazoline-2-thione (s) 4,5 -dipropyloxazoline-2-thione (s) 4,5 -diphenyloxazoline-2-thione(s) 4- (p-dimethylamino) -5-phenyloxazoline-2-thione(s) 4- (pmethoxyphenyl) -5-phenyloxazoline-2-thione (s) Tetrahydrobenzoxazoline-Z-thione( s) These compounds may be prepared according to the method described by R. Gompper in Ber. 89 (1956) p. 1762, or in a more simple way according to the methods given hereinafter.

PREPARATION 1.4,5-DIPHENYLOXAZOLINE- 2-THIONE(S) Into a 3 l. flask fitted with a condenser and a drop ping funnel is brought a solution of 145.5 g. (1.5 mols) of potassium thiocyanate in 2 1. of ethanol. To this solution cm. of hydrochloric acid (d.=1.19) are added and the precipitated potassium chloride is filtered off.

To the filtrate are then added 212 g. (1 mol) of henzoylphenyl carbinol (benzoin) and this mixture is refluxed for 24 hours. After cooling the obtained filtrate is diluted with 4 l. of water which give-s a new quantity PREPARATION 2.4- (p-METHOXYPHENYL) 5- PHENYLOXAZOLlNE-Z-THIONE S Into a 0.5 l. flask fitted with a condenser is introduced a solution of 24.2 g. of p-methoxybenzoin in 200 cm. of ethanol. To this solution are successively added a solution of 15 g. of potassium thiocyanate in 20 cm. of water and 15 cm. of concentrated hydrochloric acid (d.=1.19). This reaction mixture was refluxed for 6 hours.

After cooling the precipitate obtained was sucked off and washed with water. The residual precipitate was recrystallized from a mixture of ethanol and water (50:50).

PREPARATION 3.-4,5-DIMETHYLOXAZOLINE- 2-THIONE(S) Into a 0.5 l. flask fitted with a condenser are introduced a solution of 17.6 g. of 3-hydroxy-2-butanone (acetoin) in 200 cm. of ethanol and a solution of 29.1 g. of potassium thiocyanate in 40 cm. of water. After adding 60 cm. of concentrated hydrochloric acid (d.=1.19) the reaction mixture is refluxed for '6 hours.

After cooling the potassium chloride formed is filtered off and washed with ethanol. Thefiltrate is concentrated and.the crystals formed are sucked oil. The product is recrystallized from water. Melting point: 137 C.

PREPARATION 4.4,S-DIPROPYLOXAZOLINE- 2-THIONE( S) 5 Into a 3 l. flask fittedwith a condenser are introduced a solution of 84 g. of 5-hydroxy-4-octanone (butyroin) in 1.2 l. of ethanol and a solution of g. of potassium thiocyanate in 240 cm. of water. After adding 360 cm. of concentrated hydrochloric acid (d.=1.19), the reaction mixture is refluxed for 6 hours. After cooling, the potassium chloride formed 'is filtered oil. The filtrate is concentrated and the residue distilled in vacuum. The fraction of the boiling range 128'140 C. at 0.003 to 0.006 mm. of Hg pressure is a yellow oil which solidifies on cooling.

PREPARATION 5.TETRAHYDROBENZOXAZO- LINE-Z-THIONE (S) Into a 0.5 l. flask fitted with a condenser 11.4 g. of m-hydroxycyclohexanone are dissolved in 200 cm. of methanol. To this solution are successively added a so lution of 29 g. of potassium thiocyanate in 40 cm. of water and 60 cm. of concentrated hydrochloric acid (d.=1.19). hours. After cooling, the formed potassium chloride is Patented May 17,1966

The reaction mixture is refluxed during 6 =3 sucked off and the filtrate is evaporated. The precipitate thus obtained is sucked oh? and recrystallized from a mixture' of water and ethanol (50:50). Melting point: 154 C.

The compounds according to the present invention preferably are added to the emulsion after the second ripening or just before coating.

Instead of adding these compounds to the silver halide emulsion itself, they can also be added to a waterpermeable layer such as a gelatin covering layer or to an intermediate layer adjacent to the emulsion layer. The used emulsions may be sensitized according to a usual proc ess. They may be chemically sensitized by little quantities of sulphurous compounds such as allyl isothiocyanate, allyl thiourea, sodium thiosulfate, etc. The emulsions may also be sensitized by means of reducing agents e.g. the tin compounds described in the Belgian patent specifications 493,464 and 568,687, the imino-aminomethane sulphunic acid compounds described in the Belgian patent specification 547,323, and small quantities of noble metal compounds e.g. of gold, platinum, palladium, iridium, ruthenium and rhodium. The emulsion may also be sensitized by means of polyalkylene oxide derivatives e.g. polyethylene oxide, the molecular weight of which varying between 1000 and 20,000, condensation products of alkylene oxides with aliphatic alcohols or glycols, with cyclic dehydrated products of hexitols, with 'alkyl substituted phenols, with aliphatic carboxylic acids, with aliphatic amines and diamines, and withaliphatic amides. The condensation products may have a molecular weight of at least 700 and preferably above 1000.

In order to obtain well defined effects, these sensitizers evidently may be applied in combination, such as described e.g. in the Belgian patent specification 537,278 and in the British patent specification 727,982.

Further these compounds may be applied in optically sensitized emulsions as well as in non-optically sensitized emulsions.

In order to obtain well defined efiects, these compounds may also be used in combination with other known stabilizers, e.g. 7-hydroxy-5-alkyl-s-triazolo(2,3-a)pyrimidines e.g. in high-sensitive emulsions containing a development activator of the polyoxyalkylene type.

The compounds according to this invention may be applied to all kinds of emulsions such as silver bromide emulsions containing a considerable amount 'of silver iodide, silver bromide emulsions, silver bromide containing silver chloride emulsions, and silver chloride emulsions, thus in all the usual negative and positive kinds of photographic films and papers. Especially in emulsions of photographic paper sorts which after development are An identical light-sensitive material containing, however, no stabilizer is exposed and developed in the same way.

After treating these material in a stop-bath, washing and fixing, the following comparative fog densities. are noted:

Non-stabilized emulsion 0.61 Stabilize-d emulsion -Q. 0.06

The sensitivity and the gradation of the stabilize emulsion remained practicaly unchanged.

Example 2 To a high-sensitive silver bromo-iodide emulsion ca- 3.5 of iodide) 30 mg. of tetrahydrobenzoxazoline- 2-thione(s) are added before coating. This emulsion is coated onto a suitable support and dried. This material is stored for 5 days in a hot atmosphere with high relative humidity. After exposure and development of this material and of a comparison material as described in Example ,1, the following comparative fog densities are noted: 7

Non-stabilized emulsion -l. 1.14 Stabilized emulsion 0.53

submitted to high-glossing, the compounds according to this invention are very efiicient as antibronzinz agents.

The quantity of stabilizers may vary according to the kind of the used silver halide or a mixture thereof, the degree of ripening, the presence or the absence of other emulsion additives such as colour couplers, optical bleach ing agents, anti-oxidation agents, substances influencing the image-tone, etc. Generally the quantity of stabilizer varies between 0.001 and 0.35 g. per mol of silver halide. In some circumstances, however, eg, in order to achieve determined etfects, larger amounts may be used.

The following examples illustrate the invention, without limiting, however, the scope thereof.

Example 1 To a high-sensitive silver bromo-iodide emulsion, (ca. 3.5% of iodide) 30 mg. of 4,5-diphenyloxazole-2- thione per mol of silver thalide are added before the chemical ripening. After chemical ripening, the emulsion is coated onto an appropriate support and dried.

After storing this light-sensitive material for 36 h. in a warm and humid atmosphere, it is exposed for 4 seconds and developed for 4 minutes in a developing bath of the following composition:

Example 3 To' a high-sensitive silver bromo-iodide emulsion (ca. 3.5% of iodide) 30 mg. of 4,5-dimethyloxazoline-2- thione(s) are added before coating.- After exposure and development of this materialand of a comparison ma terial in a similar way as in Example 2, the following comparative values of fog-density are obtained:

Non-stabilized emulsion 1.14 Stabilized emulsion 0.48

Example 4 To a washed gelatine-silver' bromoiodide emulsion (98.2 mol percent of silver bromide and 1.8 mol percent of silver iodide), are added after ripening at 42 C., 350 mg. of 7-hydroxy-5-methyl-s-triazolo(2,3-a)pyrimi dine and 200 mg. of Carbowax6000 (a trade name of a polyethylene glycol having an average molecular weight of 6000, marketed by Union Carbide & Carbon, New York, N.Y.). After adding the usual ingredients, the emulsion thus obtained is coated onto a suitable support and dried. Azfter storing for 36 hours in a hot and moist atmosphere this emulsion is exposed for 4 seconds and developedfor 4 minutes in a developing bath'of the following composition:

Water to 1000 cm.

The developed images show a streaked irregular fog in the emulsion. When adding, however, to the same emulsion before coating 30 m gvof 4,5-diphenyloxazoline- 2-thione(s) per mol of silver halide, this material does not show this streaked fog after the same treatment.

Example 5 A silver chloroiodide emulsion for reproduction purposes (0.6% of iodide), having been prepared with 45 g. of silver nitrate per kg. of emulsion and sensitized for the spectral range of 500-570 m is coated onto a paper support. A strip of this material is exposed under a step-wedge and afiter processing to a visible image quickly dried by applying the material with its back-side onto the drum of a hot-glazing machine. This dried strip shows in the exposed parts, especially in the high-lights (the so-called p1umming) a disturbing bronzed appearance.

Another light-sensitive paper strip is prepared b applying onto a paper support the same chloroiodide emulsion to which, however, were added per kg. of emulsion 20 cm? of a 0.5% alcoholic solution of 4,5- diphenyloxazoline-Z-thione(s). After exposure, processing and drying as above, no trace of bronzing is stated. The improvement thus obtained is shown by the following values of the maximal density obtained by reflected incident light:

Unstabilized material 1.28 Stabilized material 1.37

We claim:

1. In a process for obtaining an image from a photographic material comprising a light-sensitive silver halide emulsion layer by imagewise exposing, developing, fixing and hot-glazing the said material, the improvement comprising incorporating in the said photographic material a compound of the formula wherein: each of R and R is a member selected from the group consisting of an alkyl group and a phenyl group.

2. In a process for obtaining an image from a photo- H2O C H:

3. Photographic material comprising a light-sensitive silver halide emulsion layer and containing a compound of the formula wherein: each of R and R is a member selected from the group consisting of an alkyl group and a phenyl group.

4. Photographic material comprising a light-sensitive silver halide emulsion layer and containing a compound of the formula 0H, 5. The process of claim 1 wherein the phenyl group is a methoxyphenyl group.

-6. The photographic light sensitive material of claim 3 wherein the phenyl group is a methoxyphenyl group.

References Cited by the Examiner UNITED STATES PATENTS 6/ 1961 Williams et al. 96-29 3/1963 Rauch et al. 96109 NORMAN G. TORCHIN, Primary Examiner. HAROLD N. BURS'PEIN, Examiner. 

1. IN A PROCESS FOR OBTAINING AN IMAGE FROM A PHOTOGRAPHIC MATERIAL COMPRISING A LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER BY IMAGE-WISE EXPOSING, DEVELOPING, FIXING AND HOT-GLAZING THE SAID MATERIAL, THE IMPROVEMENT COMPRISING INCORPORATING IN THE SID PHOTOGRAPHIC MATERIAL A COMPOUND OF THE FORMULA 